Navigational system



May 29, 1951 M. WALLACE NAVIGATIONAL SYSTEM 2 Sheets-Sheet 1 Filed April19, 194e May 29, 1951 riled April 19, 1946 M. WALLACE NAVIGATIONALSYSTEM 2 Sheets-Sheet 2 TRANSMITTER TUBE REACM/VCE Mapu/170x? SLA VEREPE' TE/P osC/L L A m@ f1?. 5 1| l2 l l w/DE @nA/0 l I AMPA /F/ERCoA/VER new ,fu TEE, i I I ll i a m I MUL r/PL /f/P E n I VEEN/7' I I IPatented May 29,1 '1.951

NAi/.1cAfricaniJ srssr-EM Mareel Wallace, Fairfield County, Cona,assigner,

iisfmesnerassignments, of one-half to -Ittmc Radio olnoratio, New ,Yorincorporation of NewYork Application April '19, 1946, Serial No.166:3;31'1

.42 Claims. (Cl. 343-112) This vimention ,relates generallievito@navigational systems and .relates :particular to navigational systemsfor indi. simultaneously the altitudes and relativezdietanoes @of a.plurality o f aircraft.

.in accordance with the present invention fan airway isdenediinztenms-.oi'oneor more pairs-,oi frecuenesl modulated iifiaste-rtransmitteretations andsIavereneaterstations.:separatedbyany-predetermined distance in the line :of the It willloesnownftha,aircraft located intermediate a mastehslave na" nd V,equipped withsuitable receiver-analyzer equipment., may determine its ownloeationwitnrespeet to tire `:toaster-,-slavePair by combining siena-.1sreceived Simultaneously fronifbothfstations, 'thesaid iooationbeinedeterrnined 1in terms `oi ireguenov proportional :to the distance-,of.tnesiratt'f-roni the slave station propose aeoordinglvto @transmitfrorn each oi a lplurality of aircraft .a fearrier :Signal on irequenovdetermined ley the altitudeoi the airoratt, and to .modulateeaenfaltitude representativeoarrier lwith a .Inode-,lation fSie-.nalderived i-irom master-s1ave pa.` andarepresentativefof the-losas tion of.the aircr. ;ft-.on theairrvay. interms of..-i.t s frequenoy- Thesignalstransmitted-from the var-ioiisforatt may terreoeived atreaoneraftior analysis: .andan-.- dieationvbyfa suitable,panoramic-receiver,l to inrovide `oontimious simultaneous 'indications toii the geographielocations-adatlieialtitudes of-allrtne eraf-t. B v means-tof suitablerenenients .of the System itis .furtherpossible to represent thealtitudes .and looationsefall the craft asrelativemdiCatQns-yvvithresnectto tne-altitude and the-1 0 cation of oneof the craft.

It is r accordingly an obj ect of rny invention V:to provide a-navigationaI ,system for Lproviding feimultaneous ,indicatiQns iaboard.an,a,ircraft .of :the relative locations .and altitudes `of :a,plurality Vof aircraft.

:It r is a yfurther 4oloieet y of `:the invention to vprovidevti-ansrnissions from a plurality of aircraft, representative in termsV.of 44the carrier frequenti? and modulation v:1i-reguency 1of `each.transmission of ,the-altitude and v:location -of the transmitting craft.Y

-It is anotheroloieot-ofn-the invention toprovide an indicator ,system`for :transmissions of the above character Vfor indicating selectivelythe. absolute or the relative altitudes of lea'clfl olfaplurality ofcraft and the vabsolute or the Irelative locations 4of each ofafpluralitygf c it.

Another 4oloieot `.of -athe- Mention/,desineeine-the provision of .a:transmittingrdeviee f o r transmit i2 Y i ting Iradis signa-ls.representative in .carrier frequenev .e =.measurab.1e-quentitv and inmodulation quengy of-1.a further measurable quan.- tty.

This invention also consists vin .certain other features yoiynonstrn.ration and the Combination and-,ar-ransement.T .hevariouselemente thereof, to be desoriloedJ illustrated the aooonmanyine.drawings and Speoioally pointed t Vthe -.anpended claims.

.e tartines.:

ntative ef sedation, and for ienals nlfiirality of remote amlatina-saineterms of lvisual indications;

Figure aseheniatie `viewof -a detail of Fier lire Tl.

:Figur-,e 13 -inustrates .sehenoatica-lly a `.master transmitterandlanrassociated slave repeater n sta.- tion, ,the .master transmitterheine frequency modulated zito provide: signals of value cin connecttionwith\-.my-inventon; .and

Figure Aiillustratesin schema-tic 'blockediagram certain details ofarreceivershown schematically in 'Figure f1 foffthe idrawfmgs.

lReferring inowspecica'llyito Figure 1 of .the drawings, whichLrepresents 'in schematic block diagram an installation --aboard anaircraft, -the numeral represents-'a `rad-io `transmitter khaving anantennal, and*Whichiisassociated with means for controlling `the jfreq-uernzly of transmission j, comprising -a reactance ltube modulator 3controll-able fin the usuale-manner in response to -control voltagesappliedeto certain elements'thereof. Gontrolvoltages'for the modulator 3are supplied by an Yaltituleereasapo'nsivle device ri, illustratedschematically `in'jigure 2 of vthe drawings and which inaygoniprise an4aneroid cellj for 4providins arneehanioal niotionpronortional to thealtitude `or atmosnherio .pressure to which the .oeil may tbe .submitted"The ineohanioal motion .of the aneroid neellrrnay.lire.translated internir of voltage -bvrneans .of .arotentiometer 6, the movablelofiwaielifrnavioe.suitablyvmeohanoally coupled totneaneroidineli' .andeleotrioallvoonnected by lead 8-to.tl'ie.r, ea ctance .tube modillator3.

Tneaneroidfoelllmavililievviseibe,noeohanioally coupled-to variablendenser Mor var-ying the tuning 5tI-.iereof in proportion Ytothemovement lof 3 the cell, the function of the condenser 9 beinghereinafter fully described.

The frequency controllable transmitter I may be modulated in amplitudeby means of a modulator I supplied with alternating signals having afrequency F, representative in value of the location of an aircraft ona,- predetermined airway. While signals representative ofvl thegeographical location of an aircraft may be derived in any of severaldifferent ways, I prefer in connection with the apparatus illustrated inFigure 1 of the drawings, to derive such signals from a mastertransmitter and slave repeater located along an airway and eachtransmitting frequency modulated signals which may be simultaneouslyreceived and translated in a properly designed receiver, at the outputof which will be provided. signals at the frequency F. Such a receiver Ihave represented by the numeral II, its associated receiving antennabeing denominated I2. The master-slave stations referred to above areillustrated schematically in Figure 3 of the drawings, adetaileddescription of the operation of the system being provided hereinafter inconnection with the explanation of that figure.

' It will now be apparent that a plurality of aircraft, flying on agiven airway, each equipped with a location receiver such as l I andwith suitable transmitting equipment responsive to the output of thereceiver II and to the altitude of each craft, and such as isillustrated in Figure 1 of the drawings, may each transmit carriersignals of frequency f representative of altitude and modulated with asignal the frequency F of which is in turn representative ofgeographical location. The various carriers may all be arranged to fallWithin a predetermined relatively limited frequency range f1 to fz andthe modulation frequencies may be arranged to fall within a relativelynarrow frequency range Fito F2.

In accordance with my invention, signals transmitted from the variousaircraft may be received aboard each of the aircraft, and theretranslated into simultaneous visual indications of the altitudes andVlocations of the various craft, by means of receiver-indicator apparatuscomprising a tunable R. F. amplifier I3, and a detector Ill fordetecting signals provided by the R. F. amplifier I3. The amplifier I3and the detector I4 are tunable insynchronism and cyclically, at anyconvenient rate, and which may be 3G or 60 cycles per second if desired,by means of a pair of rotatable tuning condensers I5 and I6 mounted foractuation by a common device such as a shaft represented schematicallyby means of the dotted line I1, and which may be driven by a motor I1a.By tuning the R. F. amplifier I3 and its associated detector I4 throughthe frequency range f1 to ,f2 inclusive, by means of the associatedrotating condensers I5 and I6, the various altitude representativecarrier frequencies originating aboard the various aircraft on theairway are received successively, detected and the detected modulationsignals F, falling in the frequency range F1 to F2 are applied to thevideo amplier I8, suitably amplified therein, limited in amplitude bymeans of the limiter I9 and thereafter applied to the discriminatorcircuit 20, for translation of each frequency F into a correspondingvoltage.

In one mode of operation of my novel apparatus the discriminator` may betuned-to a frequency midway of the range F1 to Fa, `whereby a maximumvoltage of one polarity may be derived from the discriminator inresponse Vto a frequency F1 and a maximum voltage ofv opposite polarityin response to the frequency F2, signals at the said mid-frequencyproducing zero voltage output.

The output voltages of the discriminator 20 may be applied to ahorizontal plate 2l of a cathode ray indicator 22, the opposinghorizontal plate 23 being grounded, whereby the cathode ray of theindicator may be caused to deflect an amount horizontally which is alinear function of any frequency F applied to the discriminator 20.

One vertical plate 24 of the cathode ray indicator 22 is supplied withsweep voltage by means of a mechanical sweep generator 25, which may bedriven from the shaft II, as is schematically indicated in the drawings,and which supplies a linear sweep voltage to the plate 24 in synchronismwith the tuning of the condensers I5 and I6. The sweep voltage appliedto the plate 24 varies between a predetermined negative and an equalpositive value, the middle or zero value of the sweep voltage beingaligned, in one mode of operation of my apparatus, with values ofcapacitance of condensers I5 and I6 corresponding with a frequencymidway of the carrier frequency range f1 to fz. The plate 2'! beinggrounded, the cathode ray of the indicator 22 will be caused to scanperiodically in a vertical direction, the value of the deflection at anyinstant bearing a correspondence with a frequency of the range offrequencies f1 to f2.

The cathode ray beam of the indicator 22 is normally de-intensied bymeans of intensity control grid 26 of said indicator, so that in theabsence of signals substantially no visible indications are provided.The intensity control grid 26 is coupled by means of a lead 28 to theoutput of the video amplifier I8, which provides the grid 26 withintensifying signals only in response to the presence of signals in theamplifier I8.

Upon reception of a carrier frequency f, modulated with a signal atfrequency F, the vertical position of the cathode ray beam of theindicator 22 corresponds with the value of the frequency f, by reason ofthe correspondence between the voltage supplied by the sweep generator25 and the tuning of amplifierZ I3 and detector I4. A potential issupplied by the discriminator -20 to the horizontal plate 2| of theindicator 22, the magnitude of which depends upon the value of thefrequency F, whereby a horizontal deflection of the cathode ray beam isproduced which is representative of the frequency F. At the same timethe grid 26 is supplied with intensifying voltage by the video amplierI8 and causes registration of a visible dot indication on the face ofthe indicator 22. It will be readily seen that the position of thevisible dot will correspond vertically to an altitude and horizontallyto a distancev along an airway, of a transmitting craft, and that a veryconsiderable number of such indications may be successively produced, inresponse to signals originating on a plurality of aircraft, and that dueto the phenomenon known as persistence of vision, as well as due to the'persistence of the screen of the cathode ray indicator itself, thevarious indications will be simultaneously visible.

In order to avoid blocking of the local amplifier I3, or of succeedingelements of its associated receiver, I have found it to be desirable toreduce substantially the amplitude of signals derived from localtransmitter I during the short interval in which amplifier I3 is tunedto the same freease-vea dency--as fthe transmitter I. flor.-"thi'spunpose I'couple 'to 1a `-coi-l 330 fin therL circuit`of1thenantenna 2 `which is associated fwith the transmitter I, afurther coil 3I,whichlisseonnectediby :means of-:a lead 32 :with-fatunable trap` circuit 33,ffthe tuning element 3:4 ofrwhichrepresented asa condenser, and `which 'is varied fin .synchronism with condensers l5Vand LI E `by-.means fof 'th'efsha-ft ITI, .fand the :motor `I la. :Bymaintainingstherftuning 1"of the trap 33atiallktim'esattthe:frequencyofthe amplier I3, ow of energy from thetransmitter I fto4 the amplifier I3 issubstantiallyrneduced,ithe.trapserv-ing` asfan fabsorptiontm'eans .'-for that energy. 'llhe funetiomoithe ftrans-miitter I .of'itransmitting information .bearing signals tovtequipments flocated fonother than the ilocalaircraftiissnotzmaterially :interfered with, however, since`:absorption-'oi :energy from the vtran'snfiiirter `I takes aplace'during only a small ".fraction of `the vtotal. transmittingitime.

My system, insofar as 11 have y.described-*it Thereto'fore, provides forthe atransrnission-from-1each of :.a plurality of f craftaof radio`signals representative of :altitude and :geographiclocation onanffairway, and for reception aboardeach `of .the :pluralitymf craftsy ofJtheradio signals iori'ginating fat the various craft,.andthe'ltranslation .of=..saidisig na'ls A.into visual .indications of:the absolute galtitudes andlooations -iofthe :various craft. vIt is,however., often `"desirable to :provide indications aboard:eachfcraftoftlre relativerather thanthe absolute altitudes andlocations .cof the YMarlous craft, thatwhetherrea'chmf .the variousv.craft is iabove aor below, iorward or .:abeam, :of its own position.`I :have faccord'ingly @provided means which may be selectively utilized:as Ydesired, 'for maintaining :the indication corresponding ito thealtitude rand lgenera-plaie slocation lof aeach @inra-ft at the center.of .thevieiningrscreenzofthefindicator aboard that cratt,ftheiindicati'ons corresponding to `all other craft beingt-located aboveor ibelow, to .thefleft er1-.to :the :rightrof eenteigin accordance"with .relative altitudes .or .locations of the fothercraft withxrespecttothe lcraft. bearing the indicator. 1

'I-o accomplish the taboyerpurposeil supply the freqeuncy :F which :isFntilized 'as 'a. modulating signal -to ra tunable fdisicnilninator:110,rcomprising a suitable tuning :condenser IH.. -fOutput-voltagvesfrom the -rdiscrimin-ator :40 rare flapplied to motor control circuits-2wvhichfcontrolsithe motorl VVin accordance `with the character lof thesvol-tages supplied theretorby the discrirninator circuit. .The motor'43 4in turn serves to lcontrolsthe 'adjustment of the tuning condenser`flliI, fbymeans-aoi \.a11drive shaft, represented conventionally y:bydotted lines `M.

:In .one usual `form .of the Adiscrim'inator voltages are produced intheoutput thereof @which are of Vone polarity :or-aa-nother idependingmponWhether the frequency :of A:the inpntnsigna'lfF is above or .below thefrequency-.to `which the discriminator is tuned.v.Theymotnrcontrol:circuit 42, on the .other fhandamay comprise ameanssuch as :a polarizedl relay i(not shown) .zresponsivefito theoutput of `the .fdiscriminatord forapplying suitable potential'saxnalilines i516 and switch 645 to the motor V113 toicontrolithesdirection,of irotation thereof, `.which lis'xarrangeditosbe suohias to vary the capacitance '.'offlthe 'condenser`IIFI to :a value such as :to `tune thediscrliniinatordfll lSto ftheffrequency Upon vvaccomplishinentfof ithe tuning operation ithefoutputvdltagefof'thediscrirninator becomes-zerofandfthe -motorfdbecomes-quiescent Since many devices L:and `circuits #are known 'liorautomatically tuning a tunable .dev-ice to the frequencyioffan Vinputsignal, :further v detailed illustra'tioncand descriptioniof a device.of .this 'character ksuitable :for :application to my :novel apparatusmay ib'e'fdispensed with.

The'motor y43 serves .not onlyto'varythe tuning of 'the condenser 4I butalso fsim'ilarlyito position a. condenser 4ill, .by Tmeans ofxsutab'lemechanical coupling 'indicated :conventionally as dotted lines 48, this.condenser :serving .to tune vthe discriminator 20 so that its centralfrequencyl corresponds with the frequency F being supplied fortransmission to the modulator I0. It will be clear that the horizontalbeam deflection at indicator 22 corresponding .to lthevmodulationsignal'F of its own Yilocal transmitter will at Iall .times be4locatedcentrally-ofthe viewing screen of the .indicator, and thatallotherfmodulation signals corresponding to those originating at thevarious aircraft, and representativeofthe locations thereof, will appearto the right or to the left of the locally produced indication,depending upon the relative locations of ythe -various airoraft'along`the airway with Vrespect to that of the local craft.

'In orderto provide for relative rather than absolute indications ofaltitude aboard the 4various craft it is required that the centerfrequency of 'th'e 1R. F. amplier I3 and the detector I4 be maintained'in correspondence with the frequency-of the transmitter since in-suchevent the vertical indication 'of `the cathode ray indicator 22corresponding vto thefrequency f of the transmitter I will appear alwayscentrally of the viewing screen of the indicator. `VI may accomplishthis object in a variety of ways but for the sake of simplicity I maycontrol an auxiliary condenser 9 for the tuned circuit of the amplifierI3, and asimilar auxiliary condenser Vfor the tuned circuit of thedetector I4 by means of a mechanical linkage 50 deriving its actuatingforce from the aneroidcell 5, as indicated in Figure 2 of the drawings.As the aneroid cell varies due to .changes of altitude, to vary the.control voltage applied to the'lead 8, so'likewise the tuning of theamplifier I3 and the detector i4 are varied, to maintain acorrespondence between the frequency of the transmitter I and thecentral frequency of the amplifier-detector.

Referring now to Figure 3 of the drawings for illustrative matter inconnection with the followingdescription of one mode of derivingmodulating signals representative of location, for application tomodulator IE! (Figure 1) there is illustrated a master transmitter Mr,and a slave repeater indicated generally as Sf, and comprising a slave.oscillator constrained to voperate Aat thefrequency of Ysignalsreceived thereby. Such slave repeater systems are well known in the .f

art, and selection of asuitable system for inclusion in-any actualinstallation may be left .to the-skill of the engineer. I refer torepeaters of the .character of those disclosed in Patent #2,183,562,issuedDecember 19, 1939, to Hansel] as exemplary of repeater stationsavailable for use inthe .systems of my invention.

`Thetransmitter 5,8, associated with the station Mr, is-modulated .inVfrequency by a reactance tubemodulator 5I which .is controlled in turn.by the output volt-agent the saw tooth generator 92. lnpthis :mannersignals providedby the transmitterMf are repetitively frequencymodulated in linear fashion, `over a predetermined range `offrequencies. The slave repeaterstation repeats alli-'signals impingingthereupon, and there is laccordingly provi-ded =at any reference :pointintermediate the master transmitter an'd the slave repeater, a pair ofsignals each instantaneously varying and differing in frequency by aconstant amount depending on the location of the reference point, aswill now be demonstrated.

Let us assume that the transmitter station Mf and its associated slaverepeater Si are separated by a distance D, and that a receiver, such asIl of Figure 1, is located at a distance a: from the repeater stationSr. Let us further assume that the velocity of modulation is in cyclesper microsecond. If f is the instantaneous frequency of the Signalderived from the transmitter Mr, at that same instant the frequency ofthe slave station will be where c is the velocity of light, and thisfrequency will differ from the frequency of the master station Mf by avalue corresponding to the change in frequency at the station Mr duringthe time required for electromagnetic energy to travel the distance D.

At a point intermediate stations Mf and Sf, and at a distance fromstation Sr, two frequencies will be available, one proportional to andthe other to d D a: Hl;

The difference between these frequencies is M r dt c a quantity which isindependent of the frequency of the stations Mf and Sf, and of thedistance between them and which depends only on the velocity ofmodulation the difference frequency has a constant value for any givendistance, and may be readily filtered from the products of the mixingoperation by means of a suitable filter 55, the output of the filterbeing then representative, in terms of its frequency, of the distance x.This frequency may be applied directly to the input of the modulator ls(Figure l) or, if desired, may be heterodyned or multiplied by knownmeans to some more convenient value of frequency.

What I claim and desire to secure by Letters Patent of the United Statesis:

l. In combination, a transmitter, means for measuring altitude, meansfor controlling the frequency of said transmitter responsive to saidmeans for measuring altitude, means for determining a parameter of'geographical location; and means responsive to said means fordetermining a parameter of geographical location for amplitudemodulating said transmitter with signals having frequenciesrepresentative of saidV parameter of geographical location.

2. In combination, rst means for transmiting signals at a frequencyrepresentative of altitude, second means for providing a further signalat a frequency representative of a parameter of geographical location,and means responsive to said second means for modulating said firstmeans.

3. A navigational system for a plurality of craft comprisingtransmitting means aboard each of the craft for transmitting a rstsignalv at a frequency representative of altitude, means aboard each ofthe craft for providing a second signal having a frequencyrepresentative of a parameter of geographical location of said craft,means responsive to said second means for modulating said rst signal,means aboard each of v the craft for receiving said modulated rstsignals and for translating said modulated first signals intosimultaneous indications of the altitudes and of the parameters ofgeographical locations of said plurality of craft.

4. The combination in accordance with claim 3 wherein said indicationsrepresent absolute altitudes and parameters of geographical locations.

5. The combination in accordance with claim 3 wherein said indicationsare representative of absolute parameters of geographical locations andrelative altitudes.

6. The combination in accordance with claim 3y wherein said indicationsare representative ofv relative parameters of altitudes and relativesignal representative in frequency of a param-v eter of the location ofthe aircraft along a predetermined airway, a receiver for receiving saidcarrier signals, a cathode ray indicator, and

means responsive to the output of said receiverv for controlling saidcathode ray indicator.

9. A navigational system comprising means located at each of a pluralityof locations for transmitting carrier signals at frequenciesrepresentative of the altitudes of said locations, said frequenciesfalling within a predetermined band of frequencies, means for'modulating said signals at each of said locations with modulatingsignals at frequencies representative of a parameter of the geographicalpositions of said locations, said modulating signals falling within apredetermined band of frequencies, receiver means at each of saidlocations comprising means' for scanning the band of'frequenciescomprising said carrier signals, a cathode ray indicator having at leastone deflecting means and a cathodeVA 'amiamo within a secondpredetermined band, an indicator for said signals arranged for producingan indication of said signals representative in one coordinate of acoordinate`- system of: the frequency of said first signals, andV forproducing an indication representative of the frequency of said secondsignals in another coordinate of said coordinate system, and meansoperative for maintaining at least; one of; said indications at theorigin of said coordinategsystem.

11. A combination in accordancew-itlrclaim 1'0 wherein said last' namedmeans is' operative to maintain both of said indications at said originof said coordinate system.

12. In combination, a plurality of; sources cf signals each adjustablein frequency within a first predetermined band, means for modulatingeach; of said signals., with further signals ad.- justable in frequencywithin a second predetermined band, means for receiving said signalsfrom said plurality ofI sources, means for demodulating signals receivedby said means for receiving, means for indicatingI simultaneouslyV inrespect to a. predetermined coordinatev system the values of thefrequencies of' said first signals and of said further signals, eachfirst signal and its associated further signalbeing represented as aunitaryv indication, and means for maintaining a predetermined one ofsaid signals on a base line of said system of' coordinates.

13'. A combination in accordance with claim 12 wherein means are furtherprovided for maintaining a further one` of said signals on ai furtherbase line of said system of coordinates.

14. In combination,'means for generating a first signal' at a firstfrequency within a first frequencyv band, means for generating aV secondsignal at a second frequency within a second frequency band, meansresponsive to said signals for indicating the simultaneous values ofsaid frequencies as. a unitaryy indication, and means responsive to saidsignals for maintaining said indication at a desired pair of valuesduring variation of at least one of saidl frequencies.

15. In combination, means for generating a plurality of first signals atfrequencies variable within a first bar-1d of frequencies, means forgenerating a plural-ity of further signals at frequencies variablewithin a further band of frequencies, means responsive to said first andfurther signalsy forl providing a plurality ofunitary indications eachrepresentative of' a frequency of said first signals and a frequency ofsaid further signals, and means responsive to said first and furthersignals for maintaining a preselected indication at a predeterminedvalue during variation of' at least one of the frequenciesV giving riseto said indications; y

16. In a position reporting systemY wherein a plurality of stationsmovable in respect to ranges and altitudes along a predeterminedV coursebetween two predetermined geographic locations report said ranges and'altitudes toa further station, means aboard eachfof saidmovable stationsfor deriving a measurement of itsirange with` re,- spect to one of said`predetermined geographic locations, means aboard each of said movablestations for derivingv aA measurement of'its altitude,

Vmeans for translating said measurements of range and altitude aboardeach of said craft into a transmittable signal having characteristicsrepresentative of saidrange and altitude, means for transmitting saidtransmittable signal from each of said, plurality of' movable stationsto said further station, and means at said further station for:receiving and translating said transmittedi signals. into indicationsyof the ranges and altitudes of said. plurality of movable stations.

17.' In a position reporting system, wherein a plurality of sta-monsYmovable along a predetermined: course between predetermined geographiclocations' report their ranges from one of said locations to a furtherstation, means aboard each of' said movable stations for deriving ameasurementof'its range' from said' one of said locations, means aboardeach of said. movable stations for translating said measurement into atransmittable: signal having a characteristic representative of saidrange, means aboard each of said stations forV transmitting said'signal, means at said further station for receiving said'signals and fortranslating said'i signals` as derived from all of said movablestations. into a. unitary display indication simultaneously of theranges of said movable stations from said one of'said'locations.

18. In. combination, a carrier transmitter, means. for measuringValtitude, means for controlling a. transmission characteristic of saidcarrier responsive to said means for measuring altitilde, means fordetermining: a parameter of geographical' location, 'and' meansresponsive to said meansl for determiningsaid parameter of geographicallocation for` modulating said carrier with signals having an informationbearing characteristic representative of" said geographical. location.

1'9. In combination, first means for transmit'- tingrsi'gnal's having aninformation bearing transmission characteristic representative ofaltitude, second meansforV providing a further signal having aninformation bearing characteristic representativey off a parameter ofgeographical location, and means responsive to said second means formodulating; said first means.

20. A navigational system comprising means aboard eachn of a pluralityof aircraft traveling along an airway for transmitting a, signal havingan' informationl bearing characteristic which is `representative ofthealtitude of the. aircraft. and

for modulating said signal with modulating, signals representative interms ofv an information bearing characteristic of the location of theIaircraftA along said predetermined ,airway a receiver for receiving saidsignals, a cathode ray indicator, and meansiresponsive to the output ofSaid. receiver for controlling, said, cathode rayv indicaton 21.111ycombination, a transmitter, meansfor measuring afirst measurablequantity, means for controlling: the frequencyof said transmitterresponsiye to.. said meansF for measuringY a first measurable.quantity., means, for determining a parameter of geographic location ofsaid transmitten and meansresponsive to said means for determining aparameter geographic location for `modulating said transmitter withsignals having frequencies representative of said geographic 1ocation. Y

22: In combination, first means for transmitting signals at a frequencyrepresentative of a first measurable quanti-ty, second means forproviding a further signal having an information bearing characteristicrepresentative of a param- 'l5 veter of` geographic location, and meansresponsive to said second means for modulating said first means.

23. A navigational system comprising means aboard each of a plurality ofmovable objects for transmitting a carrier signal the frequency of whichis representative of a navigational quantity pertaining to said movableobject, and for modulating said carrier with modulating signalrepresentative of a further navigational quantity pertaining to saidobject, a receiver for receiving a plurality of said carrier signals, acathode ray indicator, and means responsive to the output of saidreceiver for controlling said cathode ray indicator to indicatesimultaneously the values of said navigational quantities pertaining toa plurality of said objects.

24. In combination, a transmitter on a movable object, means formeasuring altitude of said transmitter, means for controlling thefrequency of said transmitter in response to said means for measuringaltitude, means for generating signals representative at each of aplurality of predetermined locations of a geographic parameter of saidlocation, means for receiving said signals on said movable objects andfor deriving therefrom a further signal representative of saidgeographic parameter at said movable object, and means for modulatingsaid transmitter lwith said further signal.

25. In combination, a carrier transmitter, -i

means on a first movable object for measuring altitude, means forcontrolling the frequency of said carrier in response to said means formeasuring altitude, a predetermined carrier frequency corresponding toeach altitude, means on said first movable object for determining aparameter of geographical location, means for modulating saidtransmitter with signals representative of said parameter ofgeographical location, a second movable object, kmeans aboard saidsecond movable object for measuring its altitude, a receiver on saidsecond movable object, means for tuning said receiver to receive acarrier having a frequency corresponding with the altitude of saidsecond movable object, said receiver comprising means for scanning afrequency spectrum centered on said frequency corresponding With-thealtitude of said second movable object.

26. A navigational system for a plurality of craft comprising meansaboard each of said craft for transmitting a first signal at a frequencyrepresentative of altitude, means aboard each of the craft for providinga second signal representative of a parameter of the geographicallocation of said craft, means responsive to said second means formodulating said flrst signal with said second signal, means aboard eachof the craftfor receiving said modulated first signals and fortranslating said modulated first signals into simultaneous indicationsof the altitudes and parameters of geographical locations of saidplurality of craft, said means aboard each of said craft for receivingcomprising a frequency scanning receiver for periodically scanning aband of frequencies including at least said first mentioned frequency.

Y2'7. A navigational system for a plurality of craft comprisingtransmitting means aboard each of the craft for transmitting a firstsignal at a frequency representative of altitude, means aboard each ofthe craft for providing a second signal representative of a parameter ofthe geographical location of said craft, means responsive to said secondmeans for modulating said rst signal with said second signal, meansaboard each of the craft for receiving said modulated first signals andfor translating said modulated first signals into simultaneousindications of the altitudes and parameters of geographical locations ofsaid plurality of craft, said means aboard each of said craft forreceiving comprising a frequency scanning receiver, said frequencyscanning receiver having means for establishing and maintaining areference frequency at a value corresponding with altitudes.

28. A navigational system for a plurality of craft comprisingtransmitting means aboard each of the craft for transmitting a rstsignal at a frequency representative of altitude, means aboard each ofthe craft for providing a second signal having a frequencyrepresentative of a parameter of the geographical location of saidcraft, means responsive to said second means for modulating said firstsignal, means aboard each of the craft for receiving said modulatedfirst signals and for translating said modulated first signals intosimultaneous indications of the altitudes and parameters of geographicallocations of said plurality of craft, said means aboard each of saidcraft for receiving comprising a frequency discriminating circuit formeasuring the frequency of said second signals. Y

29. A navigational system for a plurality of craft comprisingtransmitting means aboard each of the craft for transmitting a firstsignal at a frequency representative of altitude, means aboard each ofthe craft for providing a second signal representative of a parameter ofthe geographical location of said craft, means responsive to said secondmeans for modulating said first signal with said second signal, meansaboard each of the craft for receiving said modulated first signals andfor translating said modulated first signals into simultaneousindications of the altitudes and parameters of geographical locations ofsaid plurality of craft, said means aboard each of said craft forreceiving comprising a periodically frequency scanning receiver forscanning a spectrum of frequencies representative of a range ofaltitudes, said frequency scanning receiver comprising means for tuningsaid frequency scanning receiver to a central frequency representativeof altitude of said craft.

30. A navigational system for a plurality of craft comprisingtransmitting means aboard each of the craft for transmitting a firstsignal at a frequency representative of altitude, means aboard each ofthe craft for providing a second signal having a frequencyrepresentative of a parameter of the geographical location of saidcraft, means responsive to said second means for modulating said firstsignal with said second signal, means aboard each of the craft forreceiving said modulated first signals and for translating saidmodulated rst signals into simultaneous indications of the altitudes andparameter of geographical locations of said plurality of craft, saidmeans for receiving aboard each of said craft comprising a frequencydiscriminator circuit for measuring the frequency of said second signalsand means for tuning said frequency discriminator in accordance with theparameter of geographical location of said craft.

3l. A navigational system for a plurality of craft comprisingtransmitting means aboard each of the craft for transmitting a firstsignal at a frequency representative of altitude, means aboard each ofthe craft for providing a second signal having a frequencyrepresentative ofa Parti/mit@ 9i lille geographical location of saidamarres craft, means responsive tosaidisecondf means -for modulatingsaid` first signal with said second signal, means aboard each of thecraft for re'- ceiving said modulated first signals-and for translatingsaid modulatedi-lrst signals into simultane- `ous indications of thealtitudes andi parameters of geographical locations of said plurality ofcraft, saidY means aboard' each of' said craft' for receiving comprisinga frequency scanning receiver for scanning a band ofv frequenciesrepresentative of altitude, and a frequency discriminator circuit foraccepting and? measuring the fre- 'quencies of a band' of modul'atimvsignals having frequencies representative ofV geographical locasentativeof altitude, meansA aboard eachz of the craft for providing a secondsignallhavi'nga frequency representative of: the geographical locationalong saidV course of said craft, means responsive to said'secondmeansfor modulating said first signal with said second signal, meansaboard each ofthe craft for receiving said modulated first signals andfor translating-Y said modulated first signals into simultaneousindicationsof the altitudes andv geographical locations along saidcourse of saidplurality of craft, said means vaboard each ofy saidcraftforreceiving comprising a frequency scanning receiver for scanninga band' ofA frequencies representative of` altitude 'anda frequencydiscriminatorcircuit for accept'- ing: andl measuring the frequencies ofa band of signals including modulations of said' firstsignals andrepresentative of geographical locations along said course, means vfortuning said frequency scanning receiver' andsaididiscriminator cir-Ucuit,y aboard. each of said craftiin accordance with craft forproviding a second signal having a frequency representative ofV thegeographical loca- =tion alongv said course of-gsaid.` craft, means re-'s'ponsive to saidr second: meansfor modulating said first signal, meansaboard each of the craft for receiving said modulated first signals andfor translating said modulated first signals into simultaneousindications of the altitudes and geographical locations along saidcourse of said plurality of craft, said means aboard each of said craftfor receiving comprising a frequency scanning receiver for scanning aband of frequencies representative of altitude and a frequencydiscriminator circuit for accepting :and measuring the frequency of aband of modulation signals having frequencies representative ofgeographical locations along said course, and a cathode ray tubeindicator having means for generating a cathode ray beam and first andsecond deflection means for deflecting said beam, means for applyingbeam deflecting signals to said first deiiection means for delectingsaid beam in synchronism with said scanning, and means for derivingdetected output signals from said frequency discriminator circuit andfor applying said detected output signals to said second deection means.

34. A navigational system for a plurality of 'transmitting means aboardeach ofthe craft for transmitting a first s'ignal at a frequency repre-14 craftv fiying aY predetermined' course comprising transmitting meansaboard each of the craft for transmitting' ya first signal at afrequency representati've of altitude, means aboard each of the craftfor providinga second signal having a frequency representative of .thegeographical location along said course of said craft, means responsivet'osaid second means for modulating `saidfirstlr signal with said secondsignal, means aboardeach of the craft for receiving lsaid modulatedfirst signals and for translating said modulated first signals intosimultaneous indications of the altitudes and geographical locationsalong said course of said plurality of craft, said means aboard each ofvsaid craft for receiving andV translating comprising a frequencyscanning receiver for scanning a band of frequencies representa'- tive`Vof altitude and a frequency discriminator circuit for accepting andmeasuring the fre- 0 quencies of a band of signals including modulationsof said first signals representative of geographicallocations along saidcourse, and means for tuning said frequency scanning receiver and saiddiscriminator aboard each of said craft in accordance with the altitudeand geographical location thereof along said course, said means aboardeach of said craft for translating said modulated first signals intosimultaneous indication of thev altitude yand geographical locationsalong said course of'said plurality of craft comprisingj a cathode raytube indicator having means for generating fa cathode ray beam and firstand second deflection means for deflecting "said beam,A means forapplying deecting signals to said; first deflecting means for deectingsaid beam in synchronism with said scanning, and means forderivingdetected output. signals from said frequency discriminatorcircuit fand for applying said detectedY output signals to said second"deflection means.

35. InY combination, a, source of firstfsignal adinstable inV frequencywithin a, first predetermined band, means for modulating said firstsignal Withsecond signalY adjustable in frequency Within. :aV Second.`predetermined band, an. indicator for said. signals arranged. toAproduce. an indication of said signals representative in` onecoordinateV of a coordinate system of the frequency of. said firstsignal, and forproducingI an indica,- ftion, representative of thefrequencyv of said secondK signal in :another coordinate of saidcoordi.-nate system.

36. In combination, a -source of first signals adjustable in frequencyWithin a predetermined band of frequencies, first means for measuringaltitude, means responsive to said first means for measuring altitudefor determining the frequency of said first signals, means formodulating said signals with modulation representative of information, aremote receiver for receiving said signals, means for tuning said remotereceiver within said predetermined band of frequencies,

second means for measuring altitude, means responsive to said secondmeans for measuring altitude for 'actuating said means forI tuning forestablishing a, tuning of said remote receiver, said remote receivercomprising means for detecting said modulation to derive a furthersignal representative of said information, and means responsive to saidfurther signal for lvisually displaying said information and thefrequency of said first signals.

37. In combination, a first frequency modulated transmitter located at afirst point along an air- Way, a slave repeater forrepeatingtransmissions 4from said first transmitter, means for receivingsignals from said iirst transmitter and from said repeatersimultaneously, means responsive to said means for receiving comprisingmeans for combining said signals from said rst transmitter and from saidrepeater for generating a further signal having a frequencyrepresentative of a param-eter of location along said airway, atransmitter tuned in accordance Ivvith its altitude for f transmittingan altitude representative carrier, and means for modulating saidcarrier with said -further signal.

38. A telemetric system comprising a plurality of separate means eachfor transmitting a carrier -signal at a frequency representative offirst information, each of said separate means compris- -ing means formodulating the carrier transmitted .thereby with a modulation signalrepresentative of further information, a receiver for receiving saidcarriers, a cathode ray indicator, and means responsive to the signaloutput of said receiver 'for controlling said cathode ray indicator to-indcate substantially simultaneously said flrstand further informationcontained in said plurality of carriers and in said modulation signals.

39. A telemetric system comprising a plurality of separate means eachfor transmitting acarrier signal at a frequency representative-of firstinformation, each of said separate means comprising means for modulatingthe carrier transmitted thereby with a modulation signal representativeof further information, a receiver for receiving said carriers and forproviding signal output responsive thereto, a visual display indicator,and means responsive to said signal output of said receiver forcontrolling said visual display indicator to indicate substantiallysimultaneously said first and further information contained in Vsaidplurality of carriers and in said modulation signals.

` i 40. A telemetric system comprising a plurality .to indicatesubstantially simultaneously said first Vand further informationcontained in said signal output.

41. A telemetric system comprising a plurality of separate means eachfor transmitting a signal having an information bearing characteristicrepresentative of first information, each of said separate meanscomprising further means for modulating said first mentioned signal inaccordance with further information, a receiver for receiving saidsignals, a visual display indicator, and

.means responsive to the signal output of said receiver for controllingsaid visual display indicator to indicate substantially simultaneouslyall said first and further information contained in a plurality of saidsignals deriving from said plurality of separate means.

42. A telemetric system comprising a plurality of separate means eachfor transmitting a signal having an information bearing characteristicrepresentative of first information, each of said separate meanscomprising further means for modfying said first mentioned signal inaccordance with further information, a receiver for receiv- REFERENCESCITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,279,246 Podliasky et al Apr. 7,1942 2,296,041 Luck Sept. 15, 1942 2,367,907 Wallace Jan. 23, 19452,378,298 Hilferty June 12, 1945 2,378,604 Wallace June 19, 19452,403,603 Korn July 9, 1946 2,405,231 NeWhouse Aug. 6, 1946

